Centrifuge construction



July 3, 1951 J. MERRILL ET AL 2,559,453

CENTRIFUGE CONSTRUCTION Filed June 7, 1947 2 Sheets-Sheet 1 ATTORNEY July 3, 1951 J. L. MERRILL ET AL 2,559,453

CENTRIFUGE CONSTRUCTION Filed June '7, 1947 2 SheetsSheet 2 INVENTOQS John L. MerT/Y/ VI/////'am A. fioike ATTORNEY Patented July 3, 1951 CENTRIFUGE CONSTRUCTION John L. Merrill, San Francisco, and William Arms Botke, Berkeley, Calif., assignors to Merco Gentrifugal 00., San Francisco, Calif., a corporation of California Application June 7, 1947, Serial N 0. 753,301

7 Claims.

This invention relates generally to centrifuges of the type adapted particularly for the continuous separation of solid components from a feed material containing suspended solids.

In the operation of centrifuges of the above type, such as shown for example in Patents 1,923,454, 1,847,751 and 2,060,239, a problem is involved in connection with the spilling of material into the housing which encloses the rotor, instead of being properly received in the volute orpther collecting means employed. In this connection it is desirable to avoid accumulation of any considerable amount of spilled material in the lower portion of the housing, because the atomization or spraying of such material upon contact with the rotor is objectionable, particularly in that it serves to impair the efficiency of separation by dilution of the separated components. Also the power consumption of the machine is increased, and the dynamic stability of the machine is detrimentally disturbed. It is desirable to handle such spilled material in such a manner as to avoid the necessity of using supplemental pumping equipment.

It is an object of the present invention to provide a centrifuge construction which is particularly effective in handling spilled material, and which serves to effectively return such spilled material into the centrifuge rotor together with returned underflow material.

A further object of the invention is to provide a centrifuge construction as described above which will avoid use of supplemental pumping or handling means for the purpose of removing spilled material from the housing.

Another object of the invention is to provide a centrifuge construction in which the provision for returning spilled material into the rotor does not in any way interfere with the efficiency and effectiveness of the means utilized for continuously returning underflow material into the rotor.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a side elevational view partly in section and showing a machine incorporating the present invention.

Figure 2 is a diagrammatic plan view showing connections for the return of underflow discharge material to the rotor, for removal of discharged material, and for introduction of wash liquor.

Figure 3 is an enlarged sectional detail showing the lower end of the rotor impeller and the means utilized for picking up collected and spilled material.

Figure 4 is a plan detail illustrating the construction of the pick-up ring utilized in Figure 3.

Figure 5 is a cross-sectional view taken along the line 55 of Figure 1.

Figure 6 is a diagrammatic view serving to better illustrate the mode of operation of the invention.

Figure 7 is a diagrammatic view like Figure 6 but showing another embodiment of the invention.

The centrifuge illustrated in Figure 1 of the drawing consists generally of the rotor [0 carried by the vertical shaft II, and disposed within the stationary housing I2. As will be presently described the rotor is provided with various passages, including a passage for the inflow of fluid feed material, a passage for discharge of lighter centrifugall separated overflow and a passage for supplemental fluid liquid which is preferably made up of the heavier centrifugally separated discharge material or underflow. The rotor shaft H is connected by coupling l3 to the vertical shaft M of a bearing assembly IS. The bearing assembly includes a ring I! carried by the spring mounting IS.

The housing 12 can be conveniently formed of a plurality of separable sections I2a, I2b and l2c. Section l2a forms a volute chamber 2| and constitute means for receiving centrifugally separated overflow, and section |2b is formed to provide the volute chamber 22 which constitutes means for receiving underflow or heavier separated material.

The body of the rotor I0 is likewise preferably made of a number of separable annular parts, including in this instance the main part Illa, and the upper and lower conical shaped parts lb and We. Part Illa has an inner structure 23 which is attached to the lower end of the rotor shaft II. Parts 10a and 1b are retained together by suitable means such as the expansible clamping ring 24. Within the separating chamber 26 of the rotor there is a. group of spaced,

separating discs 21 such as are commonly used in centrifuges. Mounted within the outer peripheral wall 28 of the main body part Illa are the centrifugally spaced nozzles 29, each of which is provided with a discharge orifice directed back- As means for supplying fluid feed material to the rotor, a sleeve or conduit-like member 32 is disposed inwardly of the group of discs 21, and the passage within the same is downwardly divergent. The lower portion 33 of member 32 is outwardly flared. The inner wall of member 32 is provided with circumferentially spaced vanes 34, and these vanes extend from the lower side of the flared portion 33 to the upper end of member 32. Member 32 forms a passage 36 for receiving fluid feed material, and this passage connects with main chamber 26 through the passages 31 formed between the flared portion 33, and the adjacent wall of structure 23. Concentric tubes 38, 39 surround the shaft II and extend downwardly into the space 36. The space 4| between the tubes connects at its upper end with a chamber 42 which receives fluid feed material.

The rotor section lllb extends upwardly beyond the member 32, and has an upper lip 43 for the discharge of overflow or lighter centrifugally separated material. This overflow material is received in the annular chamber or volute 2|.

The lower portion ||lc of the rotor forms an impeller for the return of heavier centrifugally separated underfiow material back into the rotor. Thus the lower end of the rotor part |c is provided with an axially and downwardly faced opening 44. This opening is directly above a nozzle 46 carried by the lower part of the housing, and which as will be presently explained serves to direct a jet or solid stream or underflow material upwardly into the impeller, and through the opening 44. For convenience the opening 44 is formed in a ring 41 which is clamped to the lower body part IlJc. Referring particularly to Figure 3 it will be noted that the opening 44 within the ring 41 is upwardly divergent, and the ring is also provided with a plurality of circumferentially spaced vanes 48. These vanes have inner vertical edges, and for convenience their outer edges can be fitted within grooves provided within ring 41 as illustrated. These vanes also extend radially with respect to the axis of the rotor. I

Within the rotor part I00 and above the ring 41 are the radially extending webs or vanes 49 which serve to impart rotary velocity to returned material. spaces between the vanes 49 passes upwardly through passages to the outer annular space 52 which communicates with the main separating chamber 26, and which also communicates with the discharge nozzles 29. The inner walls of passages 5| are defined by a conical shaped member 53, which is upwardly divergent, and which is attached to the structure 23.

In that part of the rotor immediately above the ring 41 and inwardly of the vanes 49 it is desirable to provide a vane assembly 56 of the type disclosed and claimed in co-pending application Serial No. 753,302, filed June 7, 1947, which has matured into Patent 2,525,629 of October 10, 1950. This assembly consists of a plurality of circumferentially spaced and vertically extending vanes 51, having their lower ends attached to the ring 41 and their upper ends attached to the disc 58. It will be noted that these vanes are inclined to the direction of rotation, whereby material acted upon by these vanes is forced outwardly into the spaces between the vanes 49.

In operation of the above machine some centrifugally separated material discharging from The material passing through the the rotor invariably spills into the housing, instead of being delivered into the chambers 2| and 22. It will be noted that the lower portion |2c of the housing is conical shaped, whereby such spilled material is collected in the lower part of the housing and in the proximity of the lower end of the rotor. The lower end wall 6| of the housing is fitted with the nozzle 46, and it will be noted that the proportioning is such that an annular space is provided between these parts and the adjacent lowermost end of the rotor.

The material which is discharged upwardly through the nozzle 46 is customarily heavier centrifugally separated material collected in the volute 22. As shown in Figure 2 volute 22 connects with a tangential pipe 62 which in turn connects with a pipe 63, the latter being bent and connected to the space 64 directly below and communicating with the nozzle 46. A valve controlled pipe 66 is also provided for the removal of underflow material, and an additional pipe 61 connects with pipe 63 for the introduction of a supplemental wash liquid, such as fresh water. Considerable pressure is developed by the volute 22 whereby the underfiow material discharges upwardly through the orifice 46 with considerable velocity, and in the form of a relatively compact upwardly directed jet. This jet of material is received within the lower part of the rotor, and as it is deflected radially it is thrown outwardly by the vanes 51, and then given rotary velocity by the vanes 49 to effect continued movement outwardly, whereby it is eventually received with considerable pressure and velocity in the rotor space 52.

In place of a return circuit as described above. we may use a circuit including a vent box as disclosed in Peltzer 2,039,605.

The means utilized for effecting return of spilled material into the rotor, together with the returned underflow, makes use of an as'pirating action whereby the spilled and collected material is merged with the jet of material discharging upwardly from the orifice 44. In that form of the invention illustrated in Figures 1, 3 and 6 inclusive, a relatively flat ring 1| is provided, which can be formed of suitable sheet metal. The inner peripheral edge portion 12 is bent upwardly (Figure 3) and the opening 13 in the ring is slightly larger in diameter than the diameter of the orifice of nozzle 46, and slightly smaller than the opening 44 in ring 41. For example where the nozzle 46 has an orifice 2 inches in diameter and opening 44 is 2% inches in diameter, opening 13 can be 2 inches in diameter. Ring 1| is mounted stationary by suitable means such as the attaching studs 14, whereby it is held in spaced relationship with the adjacent lower wall of the housing, thus affording a space 16 for passage of the spilled and collected material. It will be noted that the mounting of ring 1| is such that the upwardly turned inner peripheral edge portion 12 is positioned intermediate the upper end of the nozzle 46, and the opposed lowermost end of the ring 41.

It is desirable, but not essential, that the outer peripheral edge portion of ring 1| be made to form directing vanes as illustrated in Figures 3 and 4. Thus the outer peripheral edge portion of the ring 1| is bent upwardly as is evident in Figure 3, and is interrupted by radial slots 11. The intervening arcuate vanes 18 have their corner portions 19 bent upwardly whereby as the collected spilled material rotates, due to rotation induced by the rotor. the vanes tend in general to deflect material into the space 16 for return into the rotor.

Operation of the centrifuge described above is as follows: Normally the machine is operated continuously with a feed material being supplied continuously through the feed chamber 42, for delivery into the separating chamber 26. Overlow material continuously discharges over the lip ,43 into the volute 2|, and heavier centrifugally separated material or underflow' discharges continuously from the nozzle 29 into the volute 22. The major part of this underflow material is continuously returned back into the centrifuge rotor through the return circuit previously described. The returned material as it enters the rotor is in the form of a solid upwardly discharging jet of material, which is forced outwardly by the vanes 51, and then acted upon by anes 49 to be delivered with considerable pressure into the rotor space 52. Because of the proximity of the inner edge 13 of the ring 1| to the peripheral surface of the upwardly discharging jet, a marked aspirating action occurs which serves to continuously suck material from the passage or space 16 below the ring 1|. Thus any spilled material collecting in space I6 is immediately sucked inwardly and merged with the upwardly discharging jet of underflow material. Vanes 48 upon the ring 41 aid in preventing any backflow of the material, and together with the vanes 51, insure effective introduction of the returned material together with collected spilled material at a proper rate and with proper pressure being applied in the discharge of this material into the space 52.

Figure 6 diagrammatically represents the aspirating action of ring H in returning spilled material into the lowerend of the rotor. The arrows indicate spilled material flowing downwardly to the lower portion of the housing, and then being aspirated through the space below the ring H, to ultimately merge with the upwardly directed jet of returned material. The amount of the collected spilled material is at a minimum and it is not brought into direct physical contact with the exterior surfaces of the rotor. Therefore dilution of the underflow and overflow with spilled material is prevented or reduced to a minimum.

Figure '7 illustrates another embodiment of the invention in which a separate passage is utilized for effecting return of the spilled material by aspirating action. In this instance a special drainage pipe or duct 8| is provided and into which the spilled material flows. This passage is connected with an upwardly extending pipe 82 which is disposed axially of the orifice 46, and which has its upper open end terminating within the impeller. In this embodiment of the invention aspirating action occurs by virtue of discharge of returned material past the upper open end of pipe 82. and therefore collected spilled material passing downwardly through duct BI is sucked upwardly through pipe 82 and merged with the upwardly discharging jet of returned material.

We claim:

1. In a centrifuge, a vertically disposed rotor arranged for discharge of centrifugally separated underflow and overflow fractions, an impeller forming the lower part of the rotor and having a lower axial opening faced downwardly, a housing surrounding the rotor, means in conjunction with the housing for collecting discharging overflow and underflow fractions, said housing forming means serving to causeunderflow material spilling into the housing from the rotor to collect in the lower part of the housing, means for delivering an upwardly directed stream of fluid material into the impeller and through said opening, and aspirating means for delivering said collected and spilled material into the impeller together with said stream of material, said aspirating means including means for conducting the'collected spillage out of physical contact with the rotor and into aspirating relation with said stream.

2. In a centrifuge, a vertically disposed rotor arranged for separate discharge of centrifugally separated underflow and overflow fractions, an impeller forming the lower part of the rotor and having a lower axial opening faced downwardly, a housing surrounding the rotor, means in conjunction with the housing for collecting the overflow fraction. annular volute means surrounding the housing and serving to receive the underflow material discharging from the rotor and to conduct the same from the housing, means for delivering a major portion of the underflow fraction received in said volute means as an upwardly directed jet into the impeller and through said downwardly faced opening, whereby underflow material is returned to the centrifuge rotor, said housing forming means serving to cause material spilling into the housing from the rotor to collect in the lower portion of the housing, and aspirating means for delivering such collected material into the impeller together with the upwardly directed jet of returned material, said aspirating means including means for conducting the collected spillage out of physical contact with the rotor and into aspirating relation with said stream.

3. In a cetrifuge, a vertically disposed rotor, the rotor being arranged for discharge of centrifugally separated overflow and underflow fractions, an impeller forming the lower part of the rotor and having a lower axial opening faced. downwardly, a housing surrounding the rotor, means in conjunction with the housing for collecting discharging overflow and underflow fractions and for removing the same from the housing, said housing forming means to cause material spilling into the same from the rotor to collect in the lower portion of the housing, means forming a nozzle extending through the lower part of the housing and serving to deliver an upwardly directed jet of material into the impeller and through said lower opening of the impeller, the walls forming said nozzle being spaced below the lower end of the impeller by an annular gap, and means disposed in said gap and below the lower end of the rotor for conducting and delivering spilled material collecting in said housing into the upwardly directed jet of material.

4. In a centrifuge as in claim 3 in which said last named means consists of a relatively flat annular ring, said ring having its central opening surrounding said upwardly discharging jet of material and having annular spacing with respect to both the lower end of the impeller and the opposed lower wall of the housing.

5. A centrifuge as in claim 3 in which said ring has its peripheral edge portion formed to provide a plurality of circumferentially spaced deflecting vanes, said vanes being bent to deflect material into the space between said ring and the adjacent lower wall of the housing.

6. In a centrifuge, a vertically disposed rotor,

7 the rotor being arranged for discharge of centrifugally separated overflow and underfiow fractions, an impeller forming the lower part of the rotor and having a lower axial opening faced downwardly, a housing surrounding the rotor, means in conjunction with the housing for collecting discharging overflow and underflow fractions and for removing the same from the housing, said housing forming means to cause material spilling into the same from the rotor to collect in the lower portion of the housing, means forming a nozzle extending through the lower part of the housing and serving to deliver an upwardly directed jet of material into the impeller and through said lower opening of the .impeller, the walls forming said nozzle being spaced below the lower end of the impeller by an annular gap, and means disposed in said gap and below the lower end of the rotor for conducting and delivering spilled material collecting 20 said nozzle, said member defining the upper side of an annular passage, the inner periphery of said passage terminating adjacent the periphery of the jet of the material, the outer part of said passage communicating with the housing and adapted to receive said spillage.

7. In a cetrifuge as in claim 6 in which the nozae is'formed to provide a raised lip, and in which said member has a raised inner peripheral edge portion to direct spillage inwardly and upwardly over said lip.

JOHN L. MERRILL. WILLIAM ARMS BOTKE.

4 REFERENCES CITED The following references arebf record in the file of this patent:

UNITED STATES PATENTS 

